(1) Field of the Invention
The present invention relates to a data transfer device for a portable telephone, and more particularly, to a data transfer device of a portable telephone to which data terminal equipment having a data transmitting/receiving function is connectable and which has a radio link provided with an information channel, a fast associated control channel and a slow associated control channel.
(2) Description of the Related Art
Reduction in size of notebook personal computers, popularization of portable information terminal equipment and like factors have widened the use of portable telephones not only as a means of vocal communication but also as a means of transferring information such as characters, data, etc.
Also, because of inexpensive portable terminal equipment, reduction in the charge for use, etc., portable telephones have rapidly come into wide use and even more diverse uses thereof are expected in the future. Especially, there is an increasing demand for portable terminal equipment to which data terminal equipment is connectable to permit data transfer from one data terminal equipment to another, and development of higher-efficiency data transfer techniques is hoped for. Among various data transfer procedures to be expected, a procedure that permits efficient data transfer while conversation is going on during a call is particularly hoped for. A need for data transfer during vocal communication arises, for example, in cases where one desires to inform the other party of his or her address or mail address during vocal communication, one desires to send a text document and then to converse with the other party while viewing the document, or one desires to transfer telephone number data stored in the memory of the portable telephone.
In conventional hardware configuration for data transfer using a portable telephone in general, the input/output port of data terminal equipment and the input/output port of the portable telephone are connected to each other by a conversion adapter (or a mobile card). The data terminal equipment and the conversion adapter are interfaced by RS-232C.
For a radio section between the portable telephone and a base station, a standard (RCR-STD-27D) designed for digital mobile telephone systems is applied. According to this standard, a communication slot in TDMA frame structure is provided with two 112-bit information channels TCH (Traffic Channel), and usually these two information channels TCH are used to transmit coded voice. In the case of transferring data with data terminal equipment connected with a portable telephone, the two information channels TCH are allocated for the transmission of transfer data.
FIG. 25 is a sequence diagram illustrating a conventional procedure for switching between telephone communication and non-telephone communication (facsimile transmission, data communication), prescribed by the standard (RCR-STD-27D) for digital mobile telephone systems. With reference to FIG. 25, the conventional procedure will be explained below on the assumption that portable telephones A1 and A2 are connected to each other via a base station B1, an exchange C1, another exchange C2, and. another base station B2.
If a need for data transfer from the portable telephone A1 to the portable telephone A2 arises during vocal communication (D1) between the portable telephones A1 and A2 via the information channels TCH, switching to the non-telephone communication is requested vocally from the portable telephone A1 to the other party, so as to have the operation mode of the portable telephone A2 switched (D2) to the non-telephone communication. The portable telephone A2 thus switched transmits an INFO (FA) message, which is a CC message of layer 3, to the network to which it is connected, thereby making a communication mode switching request (D3). An INFO (FI) message responsive to the switching request is thereafter sent from the network (D4), and on receiving this message, the portable telephone A2 enters into a non-telephone communication mode in which data transfer can be performed.
After the operation mode of the portable telephone A2 is switched to the non-telephone communication mode, switching of the portable telephone A1 to the non-telephone communication is performed (D5) so that the operation mode thereof may be switched to the non-telephone communication mode. As a result, steps D6 and D7 similar to the steps D3 and D4, respectively, are executed. In this manner, a data transfer state (D8) is established between the portable telephones A1 and A2 via the information channels TCH.
Then, when the data transfer has been completed, the operation mode of the portable telephone A1 is switched (D9) to the telephone communication mode. Consequently, steps D10 and D11 similar to the steps D3 and D4, respectively, are executed. Subsequently, the operation mode of the portable telephone A2 is switched (D12) to the telephone communication mode, and as a result, steps D13 and D14 similar to the steps D3 and D4, respectively, are executed. Thus, a vocal communication state (D15) between the portable telephones A1 and A2 via the information channels TCH is resumed.
In the conventional system, however, data transfer is carried out using the two information channels (TCH), regardless of the quantity of data to be transferred. Accordingly, a problem arises not only in that vocal communication is inconveniently not available during data transfer, but also in that, even in the case where the quantity of transfer data is small, the two information channels (TCH) are occupied and thus the data transmission efficiency is low.
Also, when a need for data transfer arises during vocal communication, the party concerned vocally informs the other party during the vocal communication that data transfer is to be started, and after the communication modes of the two parties are switched to the non-telephone communication mode, he/she starts the data transfer. To resume vocal communication after completion of the data transfer, the communication modes are switched back to the telephone communication mode. Thus, the sequence of operations involves not a few manual operations, posing a problem that difficulty arises in performing data transfer without fail and also that data transfer requires much time.
Further, the aforementioned conventional procedure provides no reliable means for the portable telephone A1 to notify the portable telephone A2 that the data transfer has been completed, thus incurring the possibility that the portable telephone A2 is erroneously switched back to vocal communication during the data transfer, or the possibility that the portable telephone A2 fails to be switched back to vocal communication for an unnecessary long time even though the data transfer has already been completed.
In the conventional system, moreover, since vocal communication is not possible during data transfer, a problem arises in that added services for a second call, such as call waiting, three-party speech, etc., are not available.